[PATCH v3 33/35] x86/bugs: Add attack vector controls for l1tf

David Kaplan
2025-01-08T20:26:03Z

Use attack vector controls to determine if l1tf mitigation is required.

Disable SMT if cross-thread attack vector option is selected.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 662573ad3e51..2e3b4d768d6b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2780,10 +2780,15 @@ static void __init l1tf_select_mitigation(void)
}

if (l1tf_mitigation == L1TF_MITIGATION_AUTO) {
- if (cpu_mitigations_auto_nosmt())
- l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
- else
- l1tf_mitigation = L1TF_MITIGATION_FLUSH;
+ if (!should_mitigate_vuln(X86_BUG_L1TF))
+ l1tf_mitigation = L1TF_MITIGATION_OFF;
+ else {
+ if (cpu_mitigations_auto_nosmt() ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_CROSS_THREAD))
+ l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
+ else
+ l1tf_mitigation = L1TF_MITIGATION_FLUSH;
+ }
}

}
--
2.34.1